1. Field of the Invention
The present invention relates to a data communication apparatus having an error correcting communication function.
2. Related Background Art
As an error correcting mode, an error correcting communication in the full-duplex operation and an error correcting communication in the half-duplex operation have been conventionally known. Especially, as to the error correcting communication in the half-duplex operation, in order to hold data sufficient to sequentially execute a communication sequence of data (picture signal) and an error correcting sequence, it is necessary to have a memory for more than a fixed memory capacity. An error correction mode (ECM) specified in CCITT, for example, should have a memory with a memory capacity of 64K bytes.
The above error correcting communication, especially the error correcting communication in the half-duplex operation should have a memory for more than a fixed memory capacity. To communicate in ECM, for example, a memory capacity of 64K bytes or more should be secured.
In a general data communication apparatus having a memory for storing data, memory sending or memory reception for data is normally performed. If a memory for 64K bytes is left unused for ECM, for example, at this time, the memory as a whole cannot be utilized.
If, however, the capacity of the unused memory is less than 64K bytes, a problem will be caused in which any communication in ECM cannot be made.
Concerning re-sending due to an error, U.S. Pat. Nos. 4,829,524 and 4,885,755 have been used, and also concerning ECM, U.S. Pat. Nos. 5,031,179 and 5,075,783 have been used.
However, the above problem at issue has not yet been solved.